Mechanical exhaust silencer



June l, 1943. H. A. SMITH I MECHANICAL EXHAUST SILENC ER Filed Aug. l5.1941 2 Sheets-Sheet l /L ATTORNEY.)

June l, 1943. H. A. SMITH MECHANICAL EXHAUST SILENGER Filed Aug. 15,1941 2 Sheets-Sheet v2 INVENTOR /f/P/W/. 5M/rsf Mrd. www W@ ATTORNEYJPatented June l, 1943 UNITED STATES PATENT 'OFFICE MECHANICAL EXHAUSTSILENCER Harry A. Smith, Garden City, N. Y.

Application August 15, 1941, Serial No. 406,960

(Cl. ISI- 64) 11 Claims.

This invention relates to noise dissipating devices for combustionengines, and has particular reference to compact mechanical apparatusfor dissipating the exhaust noises of internal combustion engines.

Mufflers of the fixed cell expansion type are too bulky for convenientinstallation in many types of vehicles or other devices powered byinternal combustion engines.

In accordance with the present invention, I have providedmechanically-actuated sound dissipating devices which are compact andare capable of handling far greater volumes of exhaust gases than priorxed cell mulers of cornparable size.

Devices of the type embodying the invention are designed to permit theready flow of exhaust gases therethrough, but to block and dissipate thelsound waves which precede the gas pressure waves because ol theirgreater speed..

More particularly, devices of the type embodying the present inventionmay include a chamber for receiving exhaust gases and sound waves and avalve mechanism which is actuated in time-phase relation to the exhaustvalves of` the engine to confine and dissipate the sound waves in thechamber but to permit the laterarriving exhaust gases to escape freelyfrom the chamber.

For a better understanding of the present invention, reference may behad to the accompanying drawings in which:

Figure 1 is a view of a typical form of device embodying the invention,shown partly broken away and partly in section to disclose detailsthereof;

Figure 2 is a View in section taken on line 2--2 of Figure l, disclosingalso an example of the time-phase relationship between the operation ofthe device and an exhaust valve of a cnc-cylinder internal combustionengine.

Figure 3 is a view, partly broken away and partly in section, of amultiple-port sound dissipating device;

Figure 4 is a view in side elevation of a modified two-stage form ofdevice embodying the invention, shown partly in section and partlybroken away; and

Figure 5 is a view taken on line 5-5 of Figure 4 disclosing, inaddition, the time-phase relationship between the second stage of thedevice and the rst stage of the device.

Referring new to Figure l of the drawings, a typical form of theinvention may include a generally cylindrical housing I0 in which ismounted a cylindrical cup-shaped element or stator II which forms achamber for receiving exhaust gases from an engine exhaust pipe I2. Theexhaust pipe I2 may be connected to a receiving chamber I3 of generallyconical or funnel shape having its larger end disposed sub- Stantiallyin alignment with the open face of the stator II. The stator II isprovided with a gas escape port Il of rectangular or any other desiredshape which cooperates with a rotary valve member or rotor I5 toestablish communication with the interior of the housing Ill when thevalve port I6 in the rotor I5 is in alignment therewith. Suitableclearances are provided between the rotor and the stator for gaspressure bleeding. The rotor I5 is fixed on the squared end II of arotatable shaft I8 which passes through a sidewall IIJa of the housingI0 and the base IIa of the chamber-forming member II. The shaft I8 issupported in a stuffing box I8 fixed to the wall I0a of the housing I0and may be driven either by the internal combustion engine (not shown)or by other means.

The stuliing box I9 may, if desired, be watercooled so as toavoid'damage by the heat of the exhaust gases.

With this construction the exhaust gases delivered through the exhaustpipe I2 will be received in the chamber III-and in the stator II, andcan escape through the port I4 when the port I6 of the rotor I5 is inalignment therewith.

The theory of operation of sound dissipating devices of the typedescribed is as follows:

It is recognized that both sound waves and gas pressure waves aregenerated by the operation of an internal combustion engine. The soundwaves, under the conditions of pressure and temperature usuallyencountered in the manifolds and exhaust pipes of such engines, have avelocity of about 1400 feet per second, whereas the oW of exhaust gasthrough the manifold and the exhaust pipe is considerably slower.Therefore, the sound waves precede the exhaust gas pressure Waves alongthe exhaust pipe.

The present device takes advantage of the difference in speed of flow ofthe exhaust gases and the rate of propagation of the sound waves and bymeans of the stator II and the rotor I5, described above, efficientlytraps and disspates the sound waves while permitting the escape oflater-arriving exhaust gases to the atmosphere without creation ofsubstantial back-pressure.

Referring now to Figure 2, as illustrative of the time-phaserelationship between the operation of the exhaust port of a one-cylinderinternal combustion engine and the operation of my sound dissipator, itwill be seen that the stator II and the rotor I5 may be disposed so thatthe valve ports I4 and I6 therein are out of alignment when the engineexhaust port opens. The sound waves which travel faster than the exhaustgas pressure waves reach the rotor I5 and the stator II while the portsI4 and I6 are out of communication. The engine exhaust port then closesand the sound waves are coniined and dissipated before the ports I4 andlbegin to come into alignment. As the slower travelling gas pressure wavereaches the stator II, the port I6 begins to come into alignment withthe port I4 as gas may ow into the housing I and thence to atmosphere.The ports I4 and I6 remain in partial or complete alignment for asuflicient length of time to permit the exhaust gases to escape and tokeep the flow resistance at a minimum. It will be understood, of course,that the rotor I moves continuously in the cycle just described. f

It should be understood that the above-described cycle may varyconsiderably depending upon a *number of factors and that the number ofgas escape ports in the sound dissipator, in

, most instances, may be more than one. As shown in Figure 3, `thestator I Ib may be provided with a plurality of ports |40l whichcooperate withr the single port IGa in the rotor Iiia. It will beunderstood that the stator 'I Ib may have a single port, while the rotorI5a may have a plurality'of ports IGa or both the rotor and stator mayhave a plurality of ports.

With a multi-cylinder engine, the operation of the exhaust valve willcause a plurality of exhaust gas surges to travel successively along theexhaust pipe, each of these surges being preceded at a continuouslyincreasing distance by its corresponding sound waves.

Under these conditions, it will be clear that a sound wave from onecylinder arriving at the noise dissipator may be followed and precededclosely by gas pressure waves fromother cylinders.v Therefore, the portorports in the sound dissipator must open and close at very shortintervals of time so that passage of the sound waves is blocked whilepermitting passage of the exhaust'gases. Y

Obviously, the timing and phasing of my'sound dissipator cannot be thesame for all internal combustion engines. After installationy of a sounddissipator of the type described above, it may be adjusted for bestresults. The adjustment of the stator I la with relation to the rotorI5a, may be accomplished by adjusting the rotated position of the shaftI8 relatively to the cam shaft of the engine or by adjusting theposition of the stator IIb. As shown in Figure 3, the stator IIb may besupported for rotary adjustment in the housing Iil by means ofoverlapping flanges I5b and IOd on the stator and housing, respectively.Likewise, the speed of rotation of the rotor I5 or I5a may be varieduntil optimum sound dissipating effect is obtained.

While devices having only one-stage, like those described above, aresatisfactory under many conditions, it may be desirable to provide twoor more sound dissipating stages in the device when it is not possibleto suitably phase one stage. For example, occasionally it may beimpossible to prevent a sound wave and a gas pressure wave from arrivingat the stator simultaneously while the ports `of the rotor and statorare aligned and, therefore, the sound wave is not dissipated in thedevice. In order to overcome this deflciency of a single stage device, asecond stage or even more stages may be added with the ports thereofarranged so that they will attenuate and finally block the passage ofthe sound wave, without preventing the escape of the more slowlymovinggas pressure waves.

As shown in Figure 4, a typical form of device having two sounddissipating stages may include an enlarged Truste-conical housing 20having an outlet 2| and two axially aligned generally cylindricalchamber-forming members or stators 22 and 23 disposed therein; Thestator 22 may be supported on the front wall 20a of the chamber and isin communication with the receiving member 24 and the exhaust pipe 25.The second chamber or stator 23 may be supported on a diaphragm orpartition 26 about midway of the housing 20 which together with thestator 23 divides the housing into two compartments.

A driveshaft 21 supported in a water-cooled bearing 28 in the end wall20h of the housing 20 carries a rotor 29 and a rotor 30 which cooperatewith the stators 23 and 22, respectively.

As illustrated,l the stator 22 is provided with an exhaust port 22a andthe cooperating rotor 3l! is provided with a single exhaust port 30a..Similarly, the stator 23 and the rotor 29 may be provided with the ports23a and 29a, respectively.

The first stage of the device including the rotor 30 and the stator 22is operated in time relationship to the exhaust valve of the motor inthe manner described above.

The second stage of the device including the stator 23 and the rotor 29is operated in accordance with the timing shown in Figure 5. In thesecond stage, the port 29a may be staggered in such a manner that itwill not be in communication with port 23a at the same time that ports22a and 30a of stage one are in communication so as to dissipate thesound pressure waves that may pass through the rst stage while the port22a is in communication with the port 30a. The staggered relationshipmust be such, however, that the exhaust gases may pass through both ofthe stages without substantial back-pressure.

It will be understood that additional stages may be included which causefurther attenuation of the sound waves without blocking the passage ofthe exhaust gas and that additional ports 22a and/or 30a, and 23a,and/or 29a may be provided as shown in Fig. 3.

While I have disclosed the invention as including rotary elements foropening and closing the ports in the sound dissipating chambers of thevarious stages, it will be understood that other types of valves may beused, if desired. For example, one or more poppet or slide valves may beused. These valves may be actuated by a cam shaft in timed relationshipto the actuation of the exhaust valves of the associated internalcombustion engine in the time-phase relation described above.Accordingly, it will be understood that the invention is susceptible toconsiderable modication in its details without departing from theinvention and that the form of the invention disclosed herein should beconsidered as illustrative only and not as limiting the scope of thefollowing claims.

I claim:

l. In a sound-dissipating device for an internal combustion enginehaving an exhaust duct, the combination of a member having walls forminga chamber communicating freely with said exhaust duct for receivingexhaust gases and sound pressure waves from said engine, a gas escapeport in a wall of said chamber, valve means for opening and closing saidport, and means for actuating said valve in timed relation to theoperation of said engine to open said port to permit gases to escapefrom said chamber only when said exhaust gases are being delivered to Ysaid chamber and to close said port to trap sound pressure Waves in saidchamber.

2. In a sound-dissipating device for an internal combustion enginehaving an exhaust duct, the combination of a member having walls formingan unobstructed chamber for receiving exhaustl gases from said duct,said member having a gas escape port in a wall thereof, valve means foropening and closing said port, and means for actuating said valve meansfor opening said port during the iiow of exhaust gases into saidchamber, oniy, to permit exhaust gases to escape from said chamber, andfor closing said port to trap and dissipate sound pressure waves in saidchamber.

3. Inra sound-dissipating device for internal combustion engines, thecombination of a housing, means having walls forming a substantiallyunobstructed chamber in said housing for receiving exhaust gas and soundpressure waves from said engine, said chamber forming means having aport in a wall thereof connecting the interior of said chamber with theinterior of said housing, valve means for opening and closing said port,and means for actuating said valve i means to open said port to permitexhaust gases to flow from said chamber into said housing during ow ofexhaust gas into said chamber and closing said port to trap anddissipate the sound pressure waves received from said engine.

4. In a sound-dissipatingr device for an internal combustion enginehaving an intermittently actuated exhaust valve and an exhaust port, thecombination of a member' having walls forming a chamber communicatingwith said exhaust port for receiving exhaust gas and sound pressurewaves therefrom, means forming a. port in a wall of said member topermit escape of gases from said chamber, valve means for opening andclosing said port, and means for actuating said valve means intime-phase relation to the intermittent actuation of said exhaust valve,to open said port to permit exhaust gas to escape through said port fromsaid chamber and to substantially close sai-d valve means to trap anddissipate said sound pressure waves in said chamber.

5. In a sound-dissipating device for internal combustion engines havingan intermittently actuated exhaust valve and an exhaust port, thecombination of a chamber communicating with said exhaust port forreceiving exhaust gas and sound pressure waves therefrom, valve meanscommunicating with said chamber, means for opening and closing saidvalve means in timephase relation to the intermittent actuation of saidexhaust valve, to open said valve means to permit exhaust gas to escapefrom said port and chamber and to substantially close said valve meansto trap and dissipate said sound pressure waves in said chamber, andmeans for adjusting the time-phase relation between said exhaust valveand said valve means.

6. In a sound-dissipating device for internal combustion engines, thecombination of a chamber for receiving exhaust gas and sound pressureWaves freely from said engine, said chamber having a port therein forallo-wing escape of exhaust gases from said chamber, a valve for closingand opening said port, and means for actuating said valve to open saidport to permit the exhaust gases received therein to escape and forclosing said port to trap and dissipate sound waves received therein.

'7. In a sound-dissipating device for an internal combustion engine, thecombination of a chamber for receiving exhaust gases and sound pressureWaves from an internal combustion engine, said chamber having at leastone gas escape port therein, rotary valve means for opening and closingsaid port, and means for rotating said valve means in time-phaserelation to Said engine to close said port intermittently to trap anddissipate sound pres-sure waves in said chamber and open said portintermittently to allow escape of exhaust gases.

8. In a sound-dissipating device for an internal combustio-n engine, thecombination of a chamber for receiving exhaust gases and sound pressurewaves from an internal combustion engine, said chamber having at leastone gas escape port therein, rotary valve means for opening and closingsaid port, means for rotating said Valve means in time-phase relation tosaid engine to close said port intermittently to trap and dissipatesound pressure waves in said chamber and open said port intermittentlyto allow escape oi exhaust gases, and means for adjusting said chamberand said rotary valve means relatively to each other to vary the phaserelationship between said Valve and said engine.

9. In a sound-dissipating device for internal combustion engines, thecombination of a housing, means forming a chamber having at least onegas escape port communicating with said housing, a rotor in said chamberhaving at least one port therein adapted to move into and out ofalignment with the port in said chamber, and means for rotating saidrotor 'to move the rotor port out of alignment with said chamber port totrap sound pressure waves from said engine and to move said rotor portinto alignment with said chamber port when exhaust gases arrive at saidchamber.

10. In a sound-dissipating device for internal combustion engines, thecombination of a housing, means forming a chamber having at least onegas escape port communicating with said housing, a rotor in said chamberhaving at least one port therein adapted to move into and out ofalignment with the port in said chamber, means for rotating said rotorto move the rotor port out of alignment with said chamber port to trapsound pressure waves from said engine and to move said rotor port intoalignment with said chamber port when exhaust gases arrive at saidchamber, and means i'or adjusting the angular relationship between saidrotor and chamber ports to vary the phasing of said ports with relationto the operation of said engine.

11. In a sound-dissipating device for internal combustion engines, thecombination oi a housing, a plurality o1 chamber forming means in anddividing said housing into a plurality of compartments, at least one gasescape port in each of said chamber forming means to permit exhaustgases to flow from one chamber into a compartment and to anotherchamber, and from said another chamber into another compartment, rotaryvalve means in each of said chambers having ports lor opening andclosing the ports in said chambers, and means ior rotating said valvemeans to open the ports in said chambers successiveiy to let said gasescape from one chamber to another, and 'to close said ports to trap anddissipate sound pressure waves in said chambers.

HARRY A. SMITH.

